As much as possible. Right now are in greenhouse under 80% shade, but grow them without shade during winter. Develop better color with more light, but having some rodent problems where I normally grow them. Rodents like to wait until the Neof are about to flower (with high value of stored energy), and then eat them to the ground. LOL Really disappointing to come find crumbs where a $200/growth Neo was about to flower. They got my Chousensetsu this year and my biggest piece of Shutenno. Grrr.
Also helps to not give too much N right before flowering; they like to do vegetative growth instead of flowering if I give them too much nitrogen. I hold back on fertilizer until I see the spikes coming, then resume normal feeding.